Piston pump

ABSTRACT

The invention relates to a piston pump having a pump housing including a plurality of pump components determining the function of the piston pump, such as a pump piston which is guided in sections, a piston return spring, and a suction and pressure valve. The piston pump also has an annular chamber which delimits the pump piston on the suction side and is designed as a compensating chamber for the liquid, a delivery chamber which delimits the pump piston on the pressure side, and an elastic sealing ring for sealing the pump piston in the direction of a pump drive chamber. To prevent leakage in the direction of the pump drive chamber, the elastic sealing ring is provided with a groove into which is inserted a spring element which presses the sealing ring against the pump piston.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase Application ofPCT/EP2012/062398, filed Jun. 27, 2012, which claims priority to GermanApplication Nos. 10 2011 080 248.7, filed Aug. 2, 2011 and 10 2012 203931.7, filed Mar. 14, 2012, the contents of such applications beingincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a piston pump, in particular for deliveringpressure medium in hydraulic brake systems with traction control.

BACKGROUND OF THE INVENTION

DE 10 2010 028 539 A1 discloses a piston pump of this type, having apump housing which has a plurality of pump components which define thefunction of the piston pump, such as a pump piston, a piston restoringspring and a suction and pressure valve, and having an annular spacewhich limits the pump piston on the suction side and is configured as areplenishment space for the fluid, and a delivery space which limits thepump piston on the pressure side. In order to seal the pump piston onthe low pressure side, an elastic sealing ring with axial prestress isarranged between a bush and a stepped bore, with the result that anaxial movement of the sealing ring, which axial movement is initiated bythe sliding movement of the pump piston, can be ruled out reliably, inorder to prevent increased wear of the sealing ring. Furthermore, asupporting ring is situated between the bush and the sealing ring and aguide band for the pump piston is situated at the end of the pumphousing, a further supporting ring being arranged in front of said guideband, with the result that the sealing ring is flanked on both sides bysupporting rings. As a result, the bush which is loaded by a spring, thetwo supporting rings and the guide band are situated in the region ofthe sealing ring, which results in considerable outlay on parts which,moreover, increases the overall length of the pump.

SUMMARY OF THE INVENTION

An aspect of the present invention provides an improved piston pump insuch a way that few components which are as compact as possible arerequired, and at the same time improved sealing is ensured along thecircumferential face of the pump piston.

According to an aspect of the invention, this is achieved for a pistonpump of the specified type by an elastic sealing ring provided with agroove, in which a spring element which presses the sealing ring ontothe pump piston is inserted.

BRIEF DESCRIPTION OF THE FIGURES

Further features and advantages of the invention are apparent in thefollowing text from the description of two exemplary embodiments usingdrawings, in which:

FIG. 1 shows a longitudinal section, arranged on a pump piston, of theessential guide and sealing elements, comprising a guide band which ispressed to the stop into the pump housing and a sealing ring which isfixed in front of said guide band in the pump housing, and, separated byan annular gap, is limited by a supporting ring which is fixed in thepump housing, and

FIG. 2 shows, in a deviation from FIG. 1, a longitudinal section of asealing ring which is pressed directly to the stop into the pump housingwith a guide band which is arranged in front of said sealing ring and isseparated from the sealing ring by an annular gap.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows details of an illustration of a piston pump in alongitudinal section, which piston pump is preferably used for conveyingpressure medium in hydraulic brake systems with traction control. Thepump housing 7 of the piston pump is depicted partially and has aplurality of pump components which define the function of the pistonpump, such as an end of a piston pump 6 which is guided in sections inan annular guide band 8, and, diametrically with respect to the guideband 8, an annular space that is configured as a replenishment space 12for the fluid, and an elastic sealing ring 1 which bears against thecircumferential face of the pump piston 6 for the leak-free sealing ofthe piston end in the direction of a piston drive space 13 which, by wayof example, accommodates an eccentric with an eccentric bearing as drivefor the pump piston. The pump piston 6 and the replenishment space 12are likewise shown only in each case in the region which is relevant tothe invention, with the result that the details which can be seen fromFIG. 1 are restricted to what is necessary.

That region of the piston pump which is not shown to the left of thepump piston 6 comprises substantially a delivery space, a pistonrestoring spring and a suction and pressure valve with the associatedsuction and pressure connectors.

In order that leak-free sealing, which remains as constant as possible,of the pump piston 6 is produced in the direction of the piston drivespace 13 during pump running, the invention provides that the elasticsealing ring 1 is provided with an axially directed, annularlycircumferential groove 3 (what is known as an annular groove) whichtherefore accommodates a spring element 2 in a manner in which it isinserted laterally, which spring element 2 presses the sealing lip ofthe sealing ring 1 onto the pump piston 6. In order to generate aconstant pressing force of the sealing ring 1 onto the circumferentialface of the pump piston 6, the spring element 2 is configured as aspreading element which generates a radial force.

In order for it to be possible to test the functional reliability of thepiston pump in dry form, that is to say without the use of hydraulicfluid, the elastic sealing ring 1 is manufactured from a material withdry running characteristics which are sufficiently satisfactory for testpurposes, for which purpose polytetrafluoroethylene (PTFE) isparticularly suitable.

According to FIG. 1, the sealing ring 1 is fixed directly between theguide band 8 and a supporting ring 4 which is pressed into the steppedbore 10 of the pump housing 7, an annular gap 5 advantageously beingprovided between the supporting ring 4 and the sealing ring 1 forunimpeded lubrication of the pump piston 6 and therefore also forlubrication of the sealing lip of the sealing ring 1 with the pressuremedium which is sucked in by the pump piston 6 via the replenishmentspace 12. A hydraulic connection is provided for piston lubrication viaan axial gap 9 which is arranged between the supporting ring 4 and thepump piston 6 and extends as far as the annular gap 5, with the resultthat, during operation of the piston pump, a lubricant connection fromthe replenishment space 12 as far as the sealing ring 1 is produced in asimple, reliable way by the axial gap 9 and the annular gap 5. Here, thebrake fluid which is usually used in hydraulic brake systems and isdelivered by the piston pump serves as a lubricant.

An alternative proposed solution of the problem which was mentioned atthe outset can be gathered from FIG. 2, according to which the sealingring 1 is then fixed directly between a bore step 11 in the pump housing7, which bore step 11 adjoins the piston drive space 13, and the guideband 8 which is pressed into the stepped bore 10 of the pump housing 7and faces the replenishment space 12. Analogously to FIG. 1, in FIG. 2an annular gap 5 is also arranged between the annular guide band 8 andthe sealing ring 1 for lubricating the pump piston 6 in the region ofthe sealing ring 1, and an axial gap is arranged between the guide band8 and the stepped bore 10, which axial gap 9 extends to the annular gap5, as a result of which a pressure medium connection is produced in areliable way between the replenishment space 12 which is filled withhydraulic fluid during operation of the piston pump and the pump piston6 which is enclosed by the sealing ring 1. In the simplest embodiment,the axial gap 9 is made as a longitudinal notch on the circumference ofthe annular guide band 8.

Analogously to FIG. 1, in the exemplary embodiment according to FIG. 2,the groove 3 is also configured as an annular groove which in each caseopens laterally into the sealing ring 1, runs around over the side faceof the sealing ring 3, and the groove opening of which faces the annulargap 5 which is advantageously exposed to the operating medium, as a ruleto the brake fluid to be delivered.

In summary, the result is particularly simple, functionally reliablepiston guidance and piston sealing on the low pressure side of the pumppiston 6, which low pressure side faces the piston drive space 13, whichpiston guidance and piston sealing, as a result of the describedconfiguration and arrangement of the sealing ring 1, of the guide band 8and of the supporting ring 4, have the following advantages:

-   -   longer leak-free pump running times,    -   improved sealing action of the sealing ring 1 in all temperature        ranges,    -   a drastic reduction in components,    -   simpler and less expensive component assembly,    -   smaller axial tolerance of the installation space of the sealing        element 1 on account of the reduced number of components        (important for the reduction of the pump wear and the        improvement of the degree of efficiency of the pump),    -   dispensing with the additional greasing/oil wetting of the        sealing element 1 for the purpose of dry running pump testing.

LIST OF DESIGNATIONS

-   1 Sealing ring-   2 Spring element-   3 Groove-   4 Supporting ring-   5 Annular gap-   6 Pump piston-   7 Pump housing-   8 Guide band-   9 Axial gap-   10 Stepped bore-   11 Bore step-   12 Replenishment space-   13 Pump drive space

1. A piston pump, for delivering pressure medium in hydraulic brakesystems with traction control, having a pump housing which a pluralityof pump components which define the function of the piston pump,including a pump piston which is guided in sections in a guide band andis pressed into the pump housing and an annular space which limits thepump piston on the suction side and is configured as a replenishmentspace for the fluid, and having a delivery space which limits the pumppiston on the pressure side, and having an elastic sealing ring which isarranged between the annular guide band and a stepped bore in the pumphousing for sealing the pump piston in a leak-free manner in thedirection of a piston drive space which is formed in the pump housing,wherein the elastic sealing ring is provided with a groove, in which aspring element which presses the sealing ring onto the pump piston isinserted.
 2. The piston pump as claimed in claim 1, wherein the elasticsealing ring is manufactured from a material with unrestricted dryrunning characteristics.
 3. The piston pump as claimed in claim 1,wherein the sealing ring is fixed in the pump housing directly betweenthe guide band and a supporting ring which is pressed into the steppedbore, an annular gap being provided between the supporting ring and thesealing ring.
 4. The piston pump as claimed in claim 3, wherein an axialgap is arranged between the supporting ring and the pump piston, whichaxial gap extends to the annular gap, as a result of which a pressuremedium connection is produced between the replenishment space and thesealing ring.
 5. The piston pump as claimed in claim 1, wherein thesealing ring is fixed directly between a bore step in the pump housingand the guide band in the pump housing, the guide band is pressed intothe stepped bore, an annular gap being provided between the guide bandand the sealing ring.
 6. The piston pump as claimed in claim 5 whereinan axial gap is arranged between the guide band and the stepped bore,the axial gap extending to the annular gap, as a result of which apressure medium connection is produced between the replenishment spaceand the sealing ring.
 7. The piston pump as claimed in claim 1, wherein,in order to generate a constant pressing force of the sealing ring ontothe circumferential face of the pump piston, the spring element isconfigured as a spreading element which generates a radial force.
 8. Thepiston pump as claimed in claim 1, wherein the groove is configured asan annular groove which opens laterally into the sealing ring, runsaround over the side face of the sealing ring, and the groove opening ofwhich faces the annular gap.
 9. The piston pump as claimed in claim 2,wherein the material with unrestricted dry running characteristics ispolytetrafluoroethylene (PTFE).